These data are used to analyze codon substitutions, typically for identifying patterns in how genetic codons mutate into one another [PMC1173088].
Based on the search results, "33K.txt" refers to in a June 2005 article published on PubMed Central (PMC) . Empirical Codon Substitution Matrix - Additional File 2 File Name: 33K.txt Description: This file contains a 64 33K.txt
It is part of the supplementary material for a study on molecular evolution and codon modeling, designed to be used alongside other matrices (observed substitution counts and transition scores) [PMC1173088]. These data are used to analyze codon substitutions,
64 matrix displaying the for empirical codon substitution [PMC1173088]. 33K.txt